The major objective of the proposed research is to investigate the activity of a number of enzymatic systems in the isolated adipocyte which are directly responsible for the amount of triglyceride stored therein. These systems include basal and catecholamine-stimulated lipolysis, lipoprotein lipase activity in the cells and whole tissue, and de novo fatty acid synthesis from carbohydrate precursors. These studies will routinely be run on cells isolated from epididymal, perirenal, mesenteric and subcutaneous adipose depots of rats ranging in weight from weanlings up to about 600g in order to obtain cells of widely varying size from each depot. In order to differentiate the effects of age from those of cell size two types of experiments will be run. In the first, cells of different size will be isolated from the above depots utilizing differential flotation techniques. In this regard, cells will be of different size but presumably at the same age. Secondly, rats will be fed a high-fat diet for 3-7 days to produce a rapid cellular hypertrophy. Metabolic activity of cells from these rats will be compared to that of comparable rats on a "normal" diet to differentiate cell-size related matabolic alterations of factors affecting adipocyte size which could provide new insights into therapeutic approvals to obesity. A second objective is to provide data on the synthesis of cholesterol in various adipose tissue depots as a function of cell size since adipose tissue represents the largest exchangeable pool of cholesterol in the body and has obvious relevance to the problem of atherosclerosis.